Field of the Invention
The present invention generally relates to a compressor, and more particularly to a valve for a hermetic compressor.
FIG. 1 shows a typical example of a hermetic compressor. Referring to FIG. 1, a reference numeral 100 denotes a casing, 200 is an electronic component unit, and 300 is a compression unit for compressing refrigerant with power supplied from the electronic component unit 200.
As shown in FIG. 1, the casing 100 has upper and lower casings 110, 120, each of which has a substantially semicircular shape. The upper and lower casings 110, 120 are coupled with each other, thereby defining a predetermined sealed space therewithin.
The electronic component unit 200 includes a stator 210 installed inside of the casing 100, a rotator 220 that rotates in electromagnetic interaction with the stator 210, and a rotary shaft 230 press-fit to the rotator 220. The rotary shaft 230 has an eccentric portion 231 provided at its lower end.
The compression component unit 300 includes a piston 310, a cylinder block 320, a cylinder head 330 and a valve device 340.
The piston 310 is linked to one end of a connecting rod 311, which is connected at its other end to eccentric portion 231 of the rotary shaft 230. The cylinder block 320 provides a cylinder 321, in which the piston 310 is positioned. Accordingly, as the rotary shaft 230 is rotated, the piston 310 reciprocates within the cylinder 321.
The cylinder head 330 is connected to the cylinder block 320. The cylinder head 330 has a refrigerant suctioning chamber 332 and a refrigerant discharge chamber 333, which are partitioned from each other by a partition 331. The refrigerant suctioning chamber 332 is connected to a suction muffler 350, while the refrigerant discharge chamber 333 is connected to a discharge muffler (not shown).
A valve 340 is disposed between the cylinder block 320 and the cylinder head 330, and as shown in FIG. 2, the valve 340 includes a valve plate 341, a suction valve 342 and a discharge valve 343.
The valve plate 341 has a refrigerant suctioning hole 341a and a refrigerant discharge hole 341b formed therein. As shown in FIG. 3, the cylinder 321 of the cylinder block 320 and the refrigerant suctioning chamber 332 of the cylinder head 330 are interconnected with each other via the refrigerant suction hole 341a, while the cylinder 321 of the cylinder block 320 and the refrigerant discharge chamber 333 of the cylinder head 330 are interconnected with each other via the refrigerant discharge hole 341b. 
The suction valve 342 is disposed on the side of valve plate 341 closest to the cylinder block 320, to selectively open the refrigerant suction hole 341a. The suction valve 342 is formed by partially cutting a suction valve sheet 342a disposed between the cylinder block 320 and the valve plate 341.
The discharge valve 343 is disposed on the side of valve plate 341 closest to the cylinder head 330 to selectively open the refrigerant discharge hole 341b. At the rear portion of the discharge valve 343, a stopper 344 and a keeper 345 are formed in sequential order to restrict the listing of the discharge valve 343.
The suction valve 342 and the discharge valve 343 open or close the refrigerant suction hole 341a and the refrigerant discharge hole 341b by being moved by the pressure in the cylinder 321, thereby causing the refrigerant of the refrigerant suctioning chamber 332 to be drawn into the cylinder 321 or causing the refrigerant of the cylinder 321 to be discharged out to the refrigerant discharge chamber 333. Such operation of the conventional valve 340 will be described below in greater detail with reference to FIG. 3.
During the stroke of the piston 310 moving from its upper dead end to its lower dead end, the suction valve 342 is moved by reduced pressure in the cylinder 321 to the position indicated by the one-dot line of FIG. 3, thereby opening the refrigerant suction hole 341a and letting the refrigerant of the refrigerant suction chamber 332 to be drawn into the cylinder 321 through the open refrigerant suction hole 341a. 
As the piston 310 is moved from its lower dead end to its upper dead end, the drawn refrigerant is compressed, and accordingly, the pressure in the cylinder 321 keeps increasing. At this time, the suction valve 342 is moved by the pressure in the cylinder 321 to the position indicated by the solid line of FIG. 3, thereby closing the refrigerant suction hole 341a. 
As the piston 310 keeps moving to its upper dead end, the pressure in the cylinder 321 also keeps increasing. Then, as the piston 310 moves very close to its upper dead end, the pressure in the cylinder 321 has increased to the maximum extent, and accordingly, the discharge valve 343 is moved by the pressure in the cylinder 321 to the position indicated by the one-dot line of FIG. 3, thereby opening the refrigerant discharge hole 341b. As a result, the compressed refrigerant in the cylinder 321 is discharged to the refrigerant discharge chamber 333 of the cylinder head 330 through the refrigerant discharge hole 341b. 
After reaching its upper dead end, the piston 310 is moved back to its lower dead end, and by the recovery force of the discharge valve 343, the discharge valve 343 is moved to the position indicated by the solid line of FIG. 3, closing the discharge hole 341b. Accordingly, as the pressure is produced in the cylinder 321, the refrigerant suction hole 341a is opened.
In the conventional valve for the hermetic compressor, when the suction valve 342 and the discharge valve 343 open and close, and especially when the discharge valve 343 closes the refrigerant discharge hole 341b, the discharge valve 343 strongly beats the valve plate 341 due to the recovery force of a neck 343a of the discharge valve 343 (see FIG. 2) and the recovery force of a bending portion 344a (see FIG. 2) of the stopper 344. The striking energy generated during the beating of the valve plate 341 is converted into an instantaneous mass energy by the uniform beating of the valve plate 341, and is then converted to vibration energy generating waves. Then, considerable noise is generated as the vibration energy is converted to negative pressure energy, generating sound waves in the air.
In the conventional valve for the hermetic compressor, additional parts like stopper 344 and the keeper 345 are employed to resiliently support the discharge valve 343 and to restrict the lifting of the discharge valve 343. Accordingly, the number of parts increases and the structure becomes complex.
Further, since a certain space has to be ensured for the stopper 344 and the keeper 345, the space for the cylinder head 330 and the refrigerant suction chamber 332 becomes narrower. Accordingly, the freedom in design is limited, like the design of the refrigerant suction hole 341a and the discharge hole 341b. 
Accordingly, it is an object of the present invention to provide a valve for a hermetic compressor capable of reducing a noise of the compressor by preventing the noise generating source, i.e., by reducing sound pressure energy coming from striking energy generated during the beating of a discharge valve on a valve plate, using sound transmission loss through a partition, which is obtained from a boundary interference between different mediums.
Another object is to provide a valve for a hermetic compressor contributing to a simpler construction with a smaller number of parts and the largest-possible space for a cylinder head, where the simpler construction is obtained by opening and closing a refrigerant discharge hole with the movement of a discharge valve in a certain space by the pressure of a cylinder, thereby omitting the need for parts like a stopper and keeper for supporting the discharge valve.
The above objects are accomplished by a valve for a hermetic compressor according to the present invention, including a valve plate disposed between a cylinder block and a cylinder head, the cylinder block having a cylinder, the cylinder head having a refrigerant suction chamber and a refrigerant discharge chamber, which are partitioned from each other by a partition, the valve plate comprising at least first, second and third plates of different thicknesses, a refrigerant suction passage for interconnecting the refrigerant suction chamber and the cylinder; and a refrigerant discharge passage for interconnecting the refrigerant discharge chamber and the cylinder, a suction valve for opening/closing the refrigerant suction passage while being moved by a pressure in the cylinder; and a discharge valve for opening/closing the refrigerant discharge valve while being moved by the pressure in the cylinder.
The first through third plates may be formed of metals of different densities. The plates may be formed of non-metals of different densities. One of the plates may be formed of a metal, while the other plates are formed of non-metals of different densities.
According to a preferred embodiment of the present invention, the refrigerant suction passage comprises: a first refrigerant suction hole formed in a first plate having a predetermined diameter; a second refrigerant suction hole formed in a second plate having a diameter narrower than the diameter of the first refrigerant suction hole; and a third refrigerant suction hole formed in the third plate and having a diameter identical to the diameter of the first refrigerant suction hole. The refrigerant discharge passage comprises: a first refrigerant discharge hole formed in the first plate and having a predetermined diameter; a second refrigerant discharge hole formed in the second plate, the second refrigerant discharge hole comprising a guide portion having a diameter greater than the diameter of the first refrigerant discharge hole, and a discharge portion partially overlapping so as to be interconnected with the guide portion; and a third refrigerant discharge hole eccentrically formed away from the first refrigerant discharge hole in a manner so as to interconnect with the discharge portion of the second refrigerant discharge hole.
The discharge valve is movably disposed inside of the guide portion of the second refrigerant discharge hole to open and close the first refrigerant discharge hole. The discharge valve is formed of a circular plate having a thickness greater than the thickness of the second valve plate, and having a diameter greater than the diameter of the first refrigerant discharge hole and smaller than the diameter of the guide portion.
According to another preferred embodiment of the present invention, the plates have one or more holes of different sizes and shapes for regulating an impedance of sound waves generated by the respective plates.